Polymerizing branch-chain hexadienes



- name all, 1950 Eugene 'r. Bishop and Robert D. Sullivan, Berkeley, Calif., assignors to Shell Development Company, San Francisco, Calif., a corporation of Delaware No Drawing. Application April 30, 1045,

' SerlaLNo. 591,220

Claims. (01. zen-$2.1)

This invention relates to the polymerization of unsaturated hydrocarbons comprising hexadienes and relates more particularly to the polymerization of branch-chain 1,3-hexadienes in -the presence of organic hydroperoxides and to the polymers thereby produced.

Processes utilized heretofore enabling the large scale production of synthetic elastomers from diene hydrocarbons are generally limited to the utilization of butadiene as starting material: In these processes the butadiene is generally polymerized alone or in admixture with another compound, such as, for example, styrene or acryldnitrile. Thoughlprocesses are now availtheless handicapped by serious disadvantages.

, The eilicient utilization, in the production of synthetic elastomers or synthetic rubbers, of dienes more readily available than butadiene and which are capable of being produced with a lesser number of operative steps substantially free of the hazards encountered in the production of butadiene, has long been sought after. Attempts to polymerize the hexadienes, particularly the 2 have a tendency to become irritating to the skin. The resultant product obtained therewith, consequently is unsuited in many of the applications in which it otherwise could be employed. Thus, benzoyl peroxide, for example, is generally considered unsuited for incorporation in packaging materials intended to enclose such item as foods or other products destined to come into direct contact with the human body. A still further disadvantage of the peroxide catalysts, particularly benzoyl peroxide. resides in the precautions which must be resorted to in handling them in even relatively pure state, as they are often subject to explosion as a result of friction or drag. Because of their ready decomposition, the resulting oxygen laden atmosphere produced is often the cause of the need for an additional inordinate degree of precautions in their ,use.

Methyl pentadiene, it has recently been found, can be utilized to a limited degree by copolymerization in admixture with a predominant amount of butadiene or other monomers. Such methods, however, still do not enable the complete elimination of butadiene in the production of elastomers of certain types, nor does it eliminate the serious disadvantages inherent in the use of the more common catalysts employed heretofore.

ployed in the polymerization of butadiene in these processes necessitate the use of a relatively low temperature which generally must not exceed about 65 C. At higher temperatures these compounds undergo substantial decomposition rendering the process inoperative or resulting in the production of a product unsuited as a commercially desirable synthetic elastomer. In this low temperature range, necessitated by the use of these catalysts, the rate of polymerization of the branched hexadienes is so slow as to render the process economically unfeasible. Attempts to polymerize the branched hexadienes above this temperature range generally do not enable the attainment of practical yields and also result in substantial decomposition of the catalysts rendering difllcult, if not impossible, the obtaining of a product having the characteristics of a synthetic elastomer or synthetic rubber of practical value.

A further disadvantage in the processes utll heretofore resides in objectional features of the catalysts often employed therein. Thus the peroxides, more readily available commercially, such as hydrogen peroxide and benzoyl peroxide,

-' charge consisting solely or predominantly of.

pentadienes, can be polymerizedat higher temperatures by resorting to the use of catalysts such as diazoamino benzene. This has enabled large scale production of valuable elastomers from a methylpentadienes. This process, however, does not enable the production of a substantially colorless product. Moreover, the-resulting product, due to the nature of the catalyst,- still renders the product unsuited for incorporation in packaging materials which must be completely non-toxic. A further disadvantage 'of the use of this type of catalyst resides in the disadvantageous effect .upon the product obtained of variations beyond a well defined limit of the hydrogen ion concentration in the reaction mixmore efllcient production of synthetic elastomers,

or synthetic rubbers, which are light in color from polymerizable monomeric materials comprising branched 1,3-hexadienes, and the synthetic elastomers thereby produced.

Another object of the invention is the provision of an improved process for the more efficient production of non-toxic, synthetic elastomers, or

synthetic rubbers, particularly suitable for incorporation in packaging materials intended for the wrapping of foods and other materials sub.- jected to intimate contact with the human body,

and the synthetic elastomers thereby produced.

The objects of the present invention are attained by the polymerization of the polymerizable monomeric material comprising a branchchain hexadiene under well defined conditions with the aid of an organic hydroperoxide, preferably a tertiary organic hydroperoxide, as catalyst.

Utilization of an organic hydroperoxide as catalyst in the process of the invention not only enables the eftlcient pglymerization of the readily available polymerizable monomeric materials consisting predominantly or solely of hexadiene,

. for example, one or more branch-chain 1,3-hexadienes with high yields in the absence of many of the disadvantages inherent in synthetic elastoalkyl, aryl, aralkyl, alkanyl, alicyclic or heterocyclic radical which may or may not be further substituted. Suitable substituted tertiary organic hydroperoxides comprise the halo-substituted organic tertiary hydroperoxides.

The tertiary alkyl hydroperoxides and substituted tertiary alkyl hydroperoxides are particularly preferred. Such particularly preferred catalysts comprise, for example, tertiary butyl hydroperoxide, their homologues and the substitution products thereof, the monohalo-substituted tertiary alkyl hydroperoxides such as chlorotertiary butyl hydroperoxide, chlorotertiary amyl hydroperoxide. and their homologues.

The tertiary organic hydroperoxides may be prepared by the slow, controlled oxidation of the corresponding organic compound containing at least one tertiary carbon atom of aliphatic character as described and claimed in copending application, Serial No. 510,421, filed November 15,

1943, now U. 8. Patent 2,403,772. The following is a non-limiting representative list of satumer producing processes utilized heretofore, but 1 eral formula R--O--O--H, wherein R is the radical R of an alcohol R-OH. By the term al-.

cohol it is intended to include broadly the primary, secondary and tertiary alcohols, which compounds may contain one or more hydroxyl groups. Included within the scope of thesuitable organic hydroperoxide catalysts are the hydroperoxides obtained by treating the corresponding alcohols with hydrogen peroxide in the presence of a suitable dehydrating agent. Alcohols which may thus be treated to obtain the hydroperoxides comprise, for example, ethanol, isopropanol, tertiary butyl alcohol, tertiary amyl alcohol, secondary butyl alcohol, monomethyl ether of ethylene glycol, monoethyl ether of ethylene glycol, propylene glypol, diethylene glycol, benzyl alcohol, cyclohexanol, cineol, 4-

methyl cyclohexanol, tetrahydrofurfuryl alcohol,

and the like. The suitable hydroperoxides are also produced by reacting neutral dialkyl sulfate with an alkali peroxide or with hydrogen peroxide in the presence of an alkali.

Of the above-definedcatalysts the tertiary organic hydroperoxides represented by the general formula R,-'-O0-H, wherein R is an organic radical which contains a tertiary carbon atom directly attached to the hydroperoxy (--0--0-H) radical are preferred. Such preferred tertiary organic compounds are suitably represented by the general formula wherein each R represents a like or different rated aliphatic hydrocarbons (containing at least one tertiary carbon atom) which are thus converted to the corresponding tertiary hydroperoxide: isobutane, 2-methyl butane, 2-ethyl butane, z-metlwl Dentane, 3-methyl pentane, 2,3- dimethyl butane, and their homologues, as well as their halogenated derivatives in which the halogen atom or atoms are attached to the primary or secondary carbon atoms so that the tertiary carbon atom or atoms contain a replaceable hydrogen atom. The following are examples of such halogenated derivatives: 1-halo-2-methyl propane, l-halo-z-ethyl propane, 1-halo-2- methyl butane,-1-'halo-3-methyl butane, and the like, and their homologues. Also, one or more of the aliphatic radicals attached to the tertiary carbon atom may be substituted by an aryl or aralkyl radical. As examples of such compounds reference may bemade to isopropyl benzene,

l-phenyl-l-methyl propane, 1-phenyl-2-methyl propane, and the like. It is to be understood, however, that the invention is in no wise limited by the method of preparation or origin of the organic hydroperoxide employed as catalyst.

Hexadienes charged to the process of the invention, particularly suited to the attainment of highly valuable synthetic elastomers or synthetic rubbers, comprise the branch-chain, 1,3-hexadienes having a straight chain of five carbon atoms. A process enabling the production of valuable synthetic elastomers from 2-methy1- 1,3-pentadiene and 4-methyl-1,3-pentadiene is particularly advantageous because of the ready availability of these hexadienes which are easily produced. According to one process of their production, acetone is first condensed to form diacetone alcohol, which is then converted to 2- methyl-2,4-pentanediol by hydrogenation, dehydration of the diol yielding the desired hexadienes. Inaccordance with the present invention 2-methyl-1,3-pentadiene and 4-methyl-1,3-

pentadiene can be polymerized alone or in admixture with one another.

.employ a charge comprising a mixture of 2- It is preferred to methyl-1,3-pentadiene and 4-methyl-1,3-pentadiene. Utilization of a mixture comprising about of 2-methyI-L3-pentadiene with about-15% of 4-methyI-L3-pentadiene, such as may be produced by the dehydration of 2-rnethyl-2,4-pentanediol is particularly preferred.

Although a particular advantage of the invention resides in the ability to produce valuable tertiary amyl hydroperoxide,

' suspension.

business I elastomers emciently from a charge consisting;

. persin'g medium. Agitation essentially only of the branch-chain hexadienes,

the invention contemplates the polymerization of mixtures comprising in addition tothe hexadiene, for example, the 2-methyl-1,3-pentadiene I orv the 4-methyl-,l,3-pentadiene, or a mixture of both, relatively lesser amounts of other polymerizable unsaturated compounds. One group of compounds which can be used in the production. of co-polymers with the methylpentadienes consists of otherpolymerizable conjugated aliphatic dienes, such-as conj ated butadiene, the con- .cellulose, poly-vinyl. alcohol, albumen, blood jugated pentadienes, etc. Particularly valuable collolymers are those ofthe methylpentadienes with minor amounts of isoprene (2-methyl-1,3-

butadiene) and with minor amounts of 1,3- butadiene. The methylpentadienes can be polymerized with minor amounts-oi compounds containing in the molecule a polymerizable unsaturated carbon-to-carbon linkage which is unconiugated with respect to carbon, 1. e. which isnot in coniugated relationship withany other polymerizable unsaturated carbon-to-carbon linkage.

Examples of polymerizable non-conjugated unsaturated compounds are styrene, alpha methyl styrene, acrylonitrile, methacrylonitrile, vinyl chloride, ,vinyl acetate, acrylates', as ethyl acrylate, methacrylates, methyl vinyl ketone, isobutylene, etc.', together with their homologues,- analogues, and suitable substitution products.

One or'more polymerizable conjugated aliphatic dienes can-be used together with one or more polymerizable'non-conjugated unsaturated compounds. The advantages of the inventionare most apparent in polymerization reactions in which the total amount of polymerizable unsaturated compounds other than the particular methylpentadienes with' which the invention is concerned is not more than about 30% by weight, preferably not more than about by weight, of 'themethylpentadiene or mixture of methyl- I pentadienes used. satisfactory'copolymers of 2- methyl-l,3-pentadiene and 4-methyl-1,3-penta-' diene with such minor proportions of other polymerizable. unsaturated compounds have not previously been capable of production on a commercially feasible scale. It is to be understood, however, that the technique of the present invention can be used in the production of co-polymers of 2-methyI-L3-pentadiene and 4-methyl- 1,3-pentadiene with more than by weight of other 'polymerizable unsaturated compounds.

The hexadiene-containing charge may be polymerized in bulk in the substantial absence of diluents. The reaction is, however, more easily controlled and the production more easily handled it a homogenizing agent is present during the polymerization. Diluent liquids employed may be solvents for the reactants and sometimes-also for the products. In general it is preferred to use diluents which are substantially non-solvents for both reactants and products, the reaction mixture being an emulsion or an impermanent will depend to some degree upon the particular promoting the production and maintenance of a dispersion which is not, however, a permanent emulsion and settles out upon cessation of agitation. The process of the invention may be executed with the reactants iu-suspension in the ab.- sence of emulsifying agents, dispersing agents, granulatlng agents and protective colloids. Such suspensions have been called zero emulsions" and the process is known as pearl polymeriza- 1on.! The reaction mixture may also contain plasticizers, anti-oxidants, inhibitors, lubricants, dyes, pigments, fillers and the like, the particular na-' ture of which is often dependent upon particular 1 conditions employed and upon the subsequenttreatmentof the reaction mixture after the polymerization and upon the characteristics of moters or regulators may be resorted to.

The polymerization of the hexadiene-containing charge is conducted in the broad range of, for example, from about 50 C. to about 150 C. Temperatures above about 80 C. are however" preferred. A particularly preferred temperature range comprises a temperature of from about 80 C. to about 120 C. Higher temperatures within the prescribed range, and even somewhat higher than 150 C., are satisfactorily resorted ,-particularly when effecting the polymerization under continuous operatingconditions.

The reaction can be conducted in a continuous or batchwise manner. -Subatmospheric, atmospheric or superatmospheric pressures up to for example about 150 pounds and higher may be used. The reaction may be carried out inthe substantial absence of free oxygen-containing the particular product desired. The use of proatmosphere. To this eilect the reaction mixture reaction is conducted and the degree of coniple- ,tion desired. In the temperature range of from .The dispersing medium employed catalyst used and should be non-reactive with the polymerizable compounds or products present in the system. Water is generally found to be a dispersing medium. Other dispersing media may, however, be used. The dispersing medium may furthermore consist of a mixture of nonsolvents, or a mixture of one or more non-solvents with one or more solvents.

The suspension or dispersion is ordinarily produced by agitation of the reactants with the disabout C. to about 120 C. a conversion of from about 75% to about of monomer to polymer is obtained in a period or! from about 5 hours to about 25 hours. Shorter or longer periods of time may however be resorted to within the scope of the invention.

The organic hydroperoxide catalyst is generally added to the reaction mixture in amounts rang ing from about 0.1% by weight to about 5% by weight, and preferably from about 0.5% to about 1.5% by weight of monomers charged. The use 75 of higher or lower amounts of the catalysts may animus.

however be resorted to. The catalyst may be added in small amounts intermittently or continuously during the course. of the polymerization reaction. It has been found that substantial ad- 'vantages are thereby obtained. Among the ad-- vantages encountered is a substantial saving in catalyst due to 'the lesser amount of catalyst empioyed. Thus in the polymerization of a mixture of; methylpentadienes consisting of a major amount of 2-methyl-l-,3-pentadiene and a' lesser amount of 4-methyl-l,3-pentadiene, when all the catalyst (tertiary butyl hydroperoxide) was added at the start of the polymerization, a con-' centration of about two parts per hundredof monomer was required to carry the reaction to a obtained with not more than 1.5parts of catalyst.

Although but one compound of the above defined class of catalysts is generally employed, more than one organichydroperoxide compound may be added as the catalyst. The catalysts are tiiene (consisting of a major proportion of 2- methyl-1,3-pentadiene and a minor proportion of 4-methyI-L3-pentadiene) containing tertiary butyl'hydroperoxideas catalyst, was emulsified in 180 parts by weight of water. Oleic acid in the amount indicated in parts by weight in the following table was added to the emulsion as an emulsifying agent. ,A protective colloid consisting of polymerized sodium saltsof alkyl naphthalene sulfonic acids, was added .inan amount equal to one part by weight. The emulsions thus obtained were maintained at the respective poly merizing temperatures and for the periods of time indicated in the table below. The amounts of catalyst, emulsifying agent, in parts by weight, as well as the yield obtained in percent by weight ofmethylpentadiene subjected to the polymerization treatment in each of the respective opera-v tions, are shown in the following table. The pH of the'emulsio'n was maintained in the range of from 10.2 to 11.5 by the addition ofaqueous sodium hydroxide to the reaction mixture during the operations. After the polymerization 'th'e It is to be pointed out thata signal advantage I of theuse of the organic-hydroperoxide catalysts Maintenance of a desired hydrogen ion concentration may be obtained by the controlled addition of suitable hydrogen ion adjusters, or buffers, such as for example, sodium 50 hydroxide phosphates, carbonates, acetals, etc. The particular range of hydrogen ion concentration to be preferred-is dependent upon many factors including the nature and properties of the reaction mixture, operating conditions, etc. when utilizing soap as the dispersing agent within the prescribed conditions of operation the hydrogen ion concentration is preferably maintained within a range of from about 10 to about 11.5 in terms of pH values.

Example I Catalyst Oleic Acid I Mooney as a gar g g gthat: y e

ar y at s y a weight weight 00 0 1;- 1.5 100 6.8 20.5 73 a 25 2 2.0 100 4.6 so. s1.5 14 a 20 :23 4.0 11 80.5 0 4. 2.0 110 4.0 ass 11 5 2.0 110 4.0 10 84.4 as o 1.5 110 4.6 17 111.4 32

added to the reactants as such or as a suspension, Example 11 or dissolved in a suitable solvent. .40

respectively, .100 parts of monomer, consisting of 80% by weight of methylpentadiene and by weight of butadiene, was emulsified in 180 parts 5 by weight of 'water. Tertiary butyl hydroperoxide was added as catalyst in the amounts indicated in the following table. 4.6 parts by weight of oleic acid, an emulsifying agent, and one part by weight of protective colloid consisting of polymerized sodium salts of alkyl naphthalene sulfonic acids were also added. The emulsions thus obtained were maintained at the respective polymerizing temperatures and for the periods or time indicated in the table below. The amounts of catalyst, in parts by weight as well as the yield in percent by weight obtainedin each of the I Catalyst Polymeri- 33?; e it t sefii limit 8T5 y re, ".119 In e weight hours 7 0.0 s 79.4 42 s 2.0 00 16 51.1 9 0.50 100 13.5 1s.0 54 0 In each of the following operations, Nos. 1

The hydroperoxide catalyzed polymers and copolymers thus obtained were found to be light in color. As compared with other synthetic rubbers, the methylpentadiene polymers and co- 5 polymers appear to possess considerable ad- The precipitated polymer was In the following operations Nos. .7 through 9,

' Ia'ua vantage in their better milling quality, tack and higher plasticity. They are soluble in most solvents, suchas, for example, in hexane, pentane, isooctane, gasoline, rubber solvent." eyclohexane, methylcyclohexane, chloroform,

ethylene dichloride, trichloroethane, trichloroethylene, monochlorobenzene, monochlorotoluene, dichlorobenzene, benzene, toluene, benzyl alcohol, dibenzyl ether, phenylethyl ether, dioxane butyl acetate,etc; v

They possess an appreciably flatter curing rate and exhibit little stiffening on over-cure. The

may be present. In tire manufacture channel black is the preferred reinforcing pigment. Semifur-containing compounds, such as sulfur dioxide,

tackiness of the elastomers of the process of the in'vention approaches that of natural rubber. They furthermore display a lower average temperature rise in hysteresis tests and have excellent aging properties; Modulus and elongations are unusually well sustained and tear and outgrowth resistance are virtually unimpaired, even after 21 days of aging. at 80 C.

When diluents are used the polymer may be precipitated or coagulated, if necessary, by known 'or special methods, separated from the remainder of the reaction mixture by filtration, centrifuging or the like, washed and dried. The polymer may be further purified by treatment, such asfor example by boiling with dilute caustic, which removes fatty acids and other contaminants which may be present. The polymer produced by aqueous emulsion methods comprises a synthetic latex which may be used directly in many applications or treated further, as by stripping, concentrating, and compounding, to increase'its usefulness reinforcing black, thermatomic black, acetylene black and the like maybeused. Mineral pigments such as clay, calcium-silicate,.iron oxide, chromay be used. I

In the production of vulcanizable compositions, one or more vulcanizing agents are usually added. Sulfur is the preferred vulcanizing agent. Other agents used, generally'with less success, are sulmium oxide, .zinc oxide, titanium dioxide, etc.

hydrogen sulfide, thiuram disulfides, tetrasulfidw and sulfur thiocyanate; oxygen and oxygen-yielding compounds, such as ozone, organic and inorganic peroxides; selenium, halogens and halo-- gen-containing compounds, and, nitrogen-con taining compounds, such as the nitrobenzenes.

vulcanization accelerators may be present. I

Illustrative examples of accelerators are tetramethyl thiuram disulfide, zinc dibutyldithiocarbamate, tetramethyl triuram monosulfide, dipentamethylene thiuram tetrasulfide, mercapto benzo thiazole, hexamethylene-tetramine, aldehyde-ammonia, diphenylguanidine, diphenylthiourea, benzo thiazyl disulflde, piperidinium .pentamethylene-dithiacorbamate, di-o-tolylguinidine, triphenylguanidine and lead dimethyldi- I thio carbamate.

In addition to, or instead of, the modifiers al- 1 ready mentioned the compositions may contain for certain applications. The dispersion medium maybe partly or whollyreplaced by another medium. Synthetic latex may alsobe produced by dispersing the coagulated polymer.

The polymers obtained-by the process of the invention maybe" compounded with modifying substances such as those used with natural rubpetroleum fractions, etc. Other plasticizers are suitable. Chemical plasticizersmay be used.

Tackiflers may be present. Among the common tackifiers are higher unsaturated cyclic ketones and hydrogenation products thereof,

resins produced by reacting. higher ketones with aldehydes, and the unsaturated hydrocarbon product obtained from lubricating oil acid sludge known commercially by the trade name "Naftolen." Antioxidants may be present. The most common antioxidant is phenyl beta-naphthyl amine.

Other antioxidants include para-hydroxy diphenyl, hydroquinone, para-amino phenol, para,- para'-diamin o diphenylmethane, 2,4-n-toluylene diamine, diaphenylamine, ortho-ditolylamine, para-ditolylamine, phenyl alpha-naphthyl amine, phenyl beta-naphthyl nitrosoamine, sym-di-betanaphthyl para-phenylene diamine, diphenyldiamino ethane and 2,4-diaminodiphenylamine.

dyes, stabilizers, lubricants, tackiflers, thickening agents, and the like. They may be mixed with plastic substances of many kinds, many of the plastics acting as plasticizers; Examples of plastic modifiers are natural resins, thermosetting condensation-type synthetic resins such as phenolaldehyde, urea-aldehyde and many alkyd resins, resins produced by the polymerization and co-polymerization of unsaturated compounds such as those listed hereinabove, protein plastics, cellulose derivatives and the like. In some cases, the'modifying plastics may be produced in situ in the presence of the polymethyl pentadienes. These and other modifiers may often be present during the polymerization reaction.

The polymers obtained in accordance with the invention may be blended with natural, synthetic or reclaimed rubber. Small amounts of latex or crude rubber of Hevea or the like increase the adhesiveness of the compositions. Synthetic rubber modifiers include polymers of'1,3-butadiene, isoprene, piperylene, 2,3-dimethyl-'1,3-butadiene, chloroprene, the other 1,3-dienes, oleflns such as isobutylene, co-polymers of 1,3-dienes with styrene, acrylonitrile and the like, co-polymers of isobutylene with a small amount of butadiene,

- high molecular weight polyesters, polyvinyl halides, olefin polysulfides andthe like.

The polyhexadiene containing polymers and compounded compositions containing them may be subjected to numerous shaping operations. Sheets may be produced by the use of roll mills such as calendars or, less usually by casting from solutions. Sheets, rods, tubes nad coatings may be produced by continuous or discontinuous extrusion. Molded articles may be produced by operations using open or closed molds. The compositions may be applied to fibrous material such as fabric by calendering or by impregnation with a solution or emulsion.

Compositions containing a vulcanizing agent may be vulcanized at temperatures used in the vulcanization of natural rubber and of other elas- C r n black and fl l r and pigments tomers, e. g. 50 0. to 200 0.

portions of the. composition thus obtained were polymerizable monomeric charge consisting of atleast one branch-chain 1.3-hexadiene having a methyl group directly attached to, a penultimate carbon atom of a straight chain of five carbon.

atoms at a temperature of from 80 C. to 150 C. in the presence of tertiary amyl hydroperoxide.

.4. A process for the production of light colored, non-toxic rubber-like materials which comprises heating in the form of an aqueous emulsion a polymerizable monomeric charge consisting of at least one branch-chain 1,3-hexadiene havinga heated at 145 C. for the periods oi timeindicated in the following table. -'The characteristics of the vulcanizates thus obtained were determined and are given in the table:

. Tensile Time oi Modulus at Permanent strength Percent Elonheating g a anon sm z e l c mga sag ng:

M...- 1,730 71 440 41 oo... 1, 6K) 010 500 32 1%.. 1,62) m 460 29 The synthetic elastomers of the invention may methyl group directly-attached to a penultimatecarbon atom of a straight chain of five carbon atoms at a temperature or from 80 C. to 150 C. in the presence; of a tertiary alkyl hydroperoxide.

5. A process for polymerizing methylpentadienes which comprises heating in the form of an aqueous emulsiona polymerizable monomeric charge consisting .of at-least one branch-chain .1,3-hexadiene having a methyl group directly attached .to .a penultimate carbon atom of a straight chain of five carbon atoms at a temperabe used for ,most of the purposes for which other synthetic and natural elastomers are used. They are valuable in the production of ballon coverings, umbreilas,. raincoats, tents, table covers. shower curtains, garment bags, electrical insulation, iriction tape, hose for the handling of aqueous mixtures, paints, etc., self-sealing fuel tanks, gaskets, belts for conveying'and for the transmission of power, vibration dampeners, printers rolls, printers blankets, engraving plates.

shoe soles and heels, aprons, gloves, gas masks, clothing resistant to the penetration of poisonous gases, tire tubes, tire casings and adhesives. They may be used as plasticizers and tackifiers.

The synthetic elastomers or synthetic rubbers produced in accordance with the process of the invention because of their non-toxic nature are, however, of particular value in the production of. or incorporation into, rubberized garments, rubber gloves, gas masks, and packaging materials for foods, drugs, and other products destined for consumption or otherwise coming into contact with the human body.

The properties of the synthetic elastomers may be modified by chemical or physical after-treatment in accordance with known or special methods.

' We claim as our invention:

1. A process for the production of light colored, non-toxic rubber-like materials which comprises heating in the form of an aqueous emulsion a polymerizable monomeric charge consisting of at least one branch-chain 1,3-hexadiene having a methyl group directlyattached to a penultimate carbon atom of a straight chain of five carbon atoms at a temperature of from 80 C. to 120 C.

ture of from 50 C. to 150 C. in the presence of atertiary alkyl hydroperoxide.

' 6. A process for polymerizinga branch-chain 1,3-hexadiene which comprises heating 'in the form of an aqueous emulsion, a polymerizable monomeric charge consisting of a branch-chain 1,3-hexadiene having a straight chain of five carbon atoms to the penultimate carbon atom of which is attached a meth 1 group at a tempera ture of from 80 C. to 150 C. in the presence of tertiary butyl hydroperoxide.

7. A process for polymerizinga branch-chain 1,3-hexadiene which comprises heating .in the formof an aqueous emulsion, a polymerizable inthe presence of from 0.1 to 5.0% by weight of monomeric charge consisting of a branch-chain 1,3-hexadiene having a straight chain of five carbon atoms to the penultimate carbon atom of which is attached a methyl group at a temperature of from C. to C. in the presence of an alkyl hydroperoxide containing a tertiary aliphatic carbon atom directly connected to the hydroperoxy radical (-0-OH).

8. A process for polymerizing a branch-chain 1,3-hexadiene which comprises heating in the form of an aqueous emulsion, a polymerizable monomeric charge consisting of a branch-chain 1,3-hexadiene having a straight chain of five carbon atoms to the penultimate carbon atom of which is attached a methyl group at a temperature of from 80 C. to 150 C.,in the presence of an alykyl hydroperoxide.

' 9. A light colored, non-toxic co-polymer of 2-methyl-1 .3-pentadiene and 4-methyl-1,3-pentadiene obtained by co-polymerizing in the iorm of an aqueous emulsion a mixture or said methylpenta'dienes at a temperature of from 80 C. to 150 C. in the presence of an alkyl hydroperoxide containing a tertiary aliphatic carbon atom directly connected to the hydroperoxide radical (,OOH).

10. A light colored, non-toxic polymer obtained by heating in the form of an aqueous emulsion a polymerizable monomeric charge consisting of at least one branch-chain 1,3-hexadiene-having amethyl group directly attached to a penultimate carbon atom of a straight chain of five carbon atoms at a temperature of from 50 C. to 150 C. in the presenceoi a tertiary alkyl hydroperoxide.

. EUGENE T. BISHOP.

ROBERT D. SULLIVAN.

7 (References on following page) 13 14 REFERENCES CITED Number Name Dat The following references are of record in the 2,391,817 Blackburn 1945 m of th patent: v 2,394,406 Schoenfeld Feb. 5, 1946 UNITED STATES PATENTS 6 2,409,996 Roedel Oct. 22, 1946 Number Name Date OTHER REFERENCES 1,294,662 Holt Feb. 18, 1919 Union Bay State 00., Chem. 8: Met: Oct. 1943, 2,142,980 Huijser Jan. 3, 1939 page 158. 2,340,109 D'Alelio Jan. 25, 1944 Bachman 8: Goebel: J. Am. Chem. Con, 64 787 2,367,805 Semple Jan. 23, 1945 to 790 (1942). 

1. A PROCESS FOR THE PRODUCTION OF LIGHT COLORED, NON-TOXIC RUBBER-LIKE MATERIALS WHICH COMPRISES HEATING IN THE FORM OF AN AQUEOUS EMULSION A POLYMERIZABLE MONOMERIC CHARGE CONSISTING OF AT LEAST ONE BRANCH-CHAIN 1,3-HEXADIENE HAVING A METHYL GROUP DIRECTLY ATTACHED TO A PENULTIMATE CARBON ATOM OF A STRAIGHT CHAIN OF FIVE CARBON ATOMS AT A TEMPERATURE OF FROM 80*C. TO 120*C. IN THE PRESENCE OF FROM 0.1% TO 5.0% BY WEIGHT OF TERTIARY BUTYL HYDROPEROXIDE. 